(Supported by NIAID R01 AI29743, R29 AI35401, NIDR K11 DE00257 to N. Charon) Spirochetes are a group of bacteria with a unique morphology. Outermost is a membrane sheath, and within this sheath is a helical-shaped cell cylinder. At each end of the cell cylinder, bacterial flagella-like organelles, called periplasmic flagella, are attached. These periplasmic flagella reside in the space between the outer membrane sheath and cell cylinder. Genetic analysis has shown that these organelles are involved in the motility of spirochetes. In addition, several lines of evidence indicate that these periplasmic flagella propel the organisms by rotation in a manner similar to bacterial flagella. The thrust of our research is centered on determining exactly how these spirochetes swim. We know that the periplasmic flagella not only play a role in motility, but also influence the shape of the cell in the domain where they reside. We used HVEM stereopairs and tilt-series mo vies to de termine the configuration of the periplasmic flagella within the organism: how they wrap around the cell cylinder, and in what direction, i.e. clockwise or counter-clockwise. The results helped us to determine how these organelles influence the shape and the motility of the organisms. Four years ago, we made a video tape of several tilt-series movies for Dr. Goldstein. Since then we have acquired improved software. The images from three tilt series were rescanned and realigned, and three new and improved movies were made. A new videotape was made which included color title panels and low-magnification still views inserted before each tilt series.